Spray Bar's

[Wayne's World]

I have finally got my 90 gal stand and hood done and the tank is being water tested now. I am planning on a relatively deep sand bed and I'm in the process of planning the flow dynamics. What is everyone doing for flow behind the rock work?? or is there no need for additional flow in that area. Due to such small sand particles is there a big problem with spray bars? I have a Wave Maker pro that will also be in the system so I was thinking of driving a spray bar with a timed power head located in the overflow. Any input would be appreciated greatly.
P.S. still looking for Southdown, anyone????????

[johnfish]

I initially came up with the idea of using a Mag 12 for internal circulation. The first idea was to divide the output with a manifold into four outlets. Thus providing the equivalent of four powerheads with one big pump. After a brief study of fluid dynamics I couldn't find a way to do this without loosing most of the flow and/or creating unbalanced flow.

The next idea was a giant spraybar made from 3/4" PVC pipe with two rows of 1/2" holes drilled at 45 degrees between the rows. An end cap was fitted on one end and the pump to the other.

The problem with this was that the holes near the end cap put out powerful jets, whereas the holes near the pump hardly passed any water at all. Go figure.

Another journey into the perplexing world of fluid dynamics revealed the problem. The water exiting the pump was a "laminar flow", which meant it was shooting past the holes in a smooth straight stream. There was no reason for the water to change direction and flow out the holes. When it hit the end cap it became a "turbulent flow", churning in all directions and exiting at the nearest holes.

The powerful flow at one end caused the fine sand in my deep sand bed to gradually migrate to one end of the tank until it was all piled up under the pump. It was like a foot deep there, but only about an inch deep at the other end. That fine sand can blow around quite easily, even when it doesn't look like it is moving.

After chatting with a Chemical Engineer at work, I found out I needed some kind of disruption inside the pipe to change the laminar flow to a turbulent flow. Small cross members just ahead of each hole was suggested. I came up with the idea of weaving air line tubing in and out of the holes. This worked pretty good; now the flow was almost even out of all the holes.

The sand was still moving about though. It wasn't as severe as before and it tended to pile up at the front of the tank and in weird little drifts. The other problem was food and stuff would gather inside the spraybar and rot.

I finally gave up on the whole idea and just went with three Maxi-Jet 1200 power heads. No further problems with shifting sands.

Cheers :)
John

[Dman]

I tried this:
http://groups.msn.com/dereksaquarium/diywavemaker.msnw
worked like a charm, until I had to clean the sprinkler heads. It was running off of a MD4QXSC and really started moving the sand around after RTN wiped out all my corals. (the corals were acting as a wave break and I removed tham after their demise) The bare spot would oscillate around the outside perimeter of the tank at the rate of one revolution every 4-5 days, rendering my DSB completely useless.
SOmeone out there has had luck with spray bars, I've tried no less than 4 different versions with varying success.
HTH
Dman
:spin: